This invention relates to water jet cutting nozzles and, in particular, relates to a nozzle having a top center feed for abrasive material and two or more fluid orifices.
It is known in the prior art to provide a nozzle assembly that receives high-pressure fluid, typically water, from an intensifier pump and has an exit orifice of small diameter to form a very thin high-pressure stream of fluid, which can be used to cut materials such as concrete and asphalt. It is also known in the prior art to introduce into the nozzle a supply of an abrasive material that is then entrained into the fluid stream exiting the nozzle to enhance the cutting action of the fluid stream. With the addition of abrasive to the fluid stream, the nozzle could even be used to cut metals. In prior art nozzles the abrasive material is introduced laterally into the fluid stream in a mixing chamber that suffers a very high rate of wear due to the bombardment of the interior of the mixing chamber walls by the abrasive material prior to and during its entrainment into the fluid stream. Also, the introduction of the abrasive into the fluid stream transverse to the fluid flow makes for a less than complete entrainment of the abrasive into the fluid stream. Because of the incomplete entrainment of the abrasive into the stream, a significant amount of the abrasive is carried on the exterior of the fluid stream and comes into contact with the walls surrounding the exit opening of the nozzle, thereby causing abrasive wear to those walls.
Some prior art water jet cutting nozzles contain jewels having a small passageway formed through them that forms the thin water stream. It is known to provide a two-piece nozzle body with the jewels mounted in one of the pieces. Typically, in the design of multiple orifice abrasive nozzles the jewels have been inserted in a single small plate and fed from a single conduit that seals the exterior of the jewel plate. In such an arrangement the abrasive must be introduced laterally into the stream downstream from the jewels. Attempts have been made to mount the jewels in an annular plate and to seal both the inner and outer periphery of the annulus and feed the high-pressure water into the annulus. The center area bounded by the annulus is then left open for an abrasive feed hole. This configuration is largely unused because of the loss of center support structure to react to the high load produced by the fluid pressure on the exposed annulus.
It is therefore an object of the present invention to provide a water jet cutting nozzle that accepts high-pressure fluid and forms the fluid into a thin exit stream and also accepts an abrasive material that is entrained and that minimizes wear at the point of mixing of the fluid and abrasive.
It is a further object of this invention to provide such a water jet cutting nozzle in which the abrasive is more fully entrained into the fluid stream and in which the contact between the abrasive and the sidewalls surrounding the exit opening of the nozzle is minimized.
It is another object of this invention to provide such a water jet cutting nozzle that can be effectively sealed against the high pressures of fluid encountered in hydraulic cutting equipment.